For selectively dispensing doses of fluid, in particular pharmaceutical powder, from an inhaler, it is general practice to use pre-dosed reservoirs known as blisters. Each blister contains one dose of fluid, and one dose of fluid is dispensed each time the inhaler is actuated. The blisters can be formed as blister packs comprising a plurality of blisters, and it has already been proposed to make the blister packs in the form of an elongate strip or a disk. A problem that is posed relates to the displacement of the blister pack in order to bring, on each actuation, a blister into a position to be opened in order to make it possible to dispense the fluid contained therein. The accuracy of the displacement and of the positioning of the blister pack is paramount in providing safe and reliable operation and metered-dose accuracy, in particular at the end of the cycle of the inhaler, i.e. when the last doses are dispensed. In particular in the context of a longitudinal strip or tape, said strip or tape can be made up of one or more layers of relatively deformable material(s). In order to displace said tape, a fairly substantial force is applied thereon, and the deformable character of the tape or of the blister strip means that the tape risks deforming with increasing advance force being exerted thereon. Such deformation can be prejudicial to the accuracy with which the tape is positioned, in particular at the end of the cycle, with it being possible that the above-mentioned drawbacks might appear. A means of solving that problem is to make the blister packs with holes or perforations in the lateral edges of said blister pack, with one or more sprocket wheels coming to penetrate into said perforations so as to cause the blister pack to advance on each actuation, somewhat like a film in a camera. However, that embodiment implies several drawbacks. Firstly, it requires the width of the blister pack to be increased, so as to enable said holes to be made. Unfortunately, the bigger the blister pack, the bigger the inhaler must also be in which said blister pack is mounted, and this can be a drawback in terms of bulkiness, complexity, and thus the cost of manufacturing the assembly. In addition, problems are posed as a result of having to make perforations in a blister pack that might comprise a plurality of layers, some of which are rather strong, e.g. aluminum layers. Thus, when some layers of the multilayer blister packs are relatively strong, the spikes used to make said holes can erode in operation in contact with the strong layers, which can cause said holes to be made less accurately and can thus cause the inhaler to malfunction. Making such lateral holes also requires the use of a complex punching system, and this increases the cost of manufacturing said blister pack.
Document EP-A-0 467 172 discloses a blister strip including lateral profiles on either side of said strip forming a plurality of notches.
Documents WO-A-01/72605 and U.S. Pat. No. 5,497,763 disclose blister packs including a blister support in the form of a strip provided with holes or perforations made in lateral edges. In such an event, one or more sprocket wheels penetrate into said perforations so as to cause the blister pack to advance on each actuation.